Inhalers are used to deliver drugs into a patient's lungs. Typically, an inhaler contains or provides a mixture of drug particles and air or propellant gas. The mixture is delivered via the patient inhaling from a mouthpiece on the inhaler with the air carrying the drug particles into the patient's lungs.
In dry powder inhalers, the drug particles, in the form of a fine dry powder, are entrained into an airflow, and inhaled by the patient, for treatment for various conditions, for example, bronchial asthma. Drugs delivered via a dry powder inhaler can be used to treat many conditions, including those unrelated to lung conditions, via the systemic absorption of the drug into the bloodstream, via the lung.
For effective dose delivery using a dry powder inhaler, the powder particles must first be dispersed to form a powder/air aerosol. Various techniques for forming powder aerosols have been proposed. One advantageous technique is described in U.S. Pat. No. 6,427,688 and International Application No. PCT/US01/03248.
While certain drugs, such as asthma drugs, may be taken several times daily, other drugs, including certain peptides or proteins, are typically taken less frequently. Due to the delay in using these types of drugs after they are removed from their packaging, providing a large number of doses within a single package is not desirable, as some doses may become unusable due to exposure to the environment. In addition, many drugs are susceptible to a short shelf life when removed from a foil storage pouch or other sealed container, even under nominal environmental conditions. These types of drugs must be used almost immediately after being exposed to the environment. Various other drugs are also most often taken only in a single or a few dose. These may include vaccines, antidotes, pain reducers, anti venoms, as well as many others. Unit dose inhalers are also useful for single dose treatments, non-chronic applications, controlled or very expensive drugs where large quantities of drug would not be acceptable, or for drugs where overdose or abuse would have serious consequences. Unit dose inhalers may also be advantageous for children where providing them with a single dose only avoids the potential for overdosing.
Inhalation provides several advantages over other delivery techniques such as oral delivery via the mouth or intravenous delivery using a syringe. Inhalation is fast, patient friendly, non-invasive, and can provide rapid absorption into the body. While unit dose inhalers have been proposed in the past, they have met with only varying degrees of success due to performance or other factors. Accordingly, there is a need for an improved unit or single dose inhaler for efficiently providing a prepackaged single dose of a powdered drug.